Manganese in pool water
Pool water problem - manganese
Although uncommon, manganese causes pool water problems that are usually difficult to identify for people with no experience of this problem.
Manganese in the pool can result in discoloration of the pool water. The water generally does not lose its clarity or become cloudy.
As the manganese is oxidized (by the chlorine, non-chlorine shock . . . ) the water darkens to a deep purple, blue or black color. So a newly filled pool may be perfectly clear and sparkling blue until chlorine is added, when almost instantly the water darkens.
Superchlorination will oxidize the manganese completely and allow it to settle to the bottom of the pool, where it can then be vacuumed out. The "rust" that settles should be vacuumed soon and the filter cleaned promptly, as the manganese sometimes has a tendency to stick.
Manganese can result in stains on the pool surfaces, especially on plaster, pebble-tec, marcite and tile grouting. The stains are usually purple or black, making the affected areas extremely unsightly.
If the fill water or make up water contains high levels of manganese, a regular treatment with a commercial metal-out or ion stabilizer is necessary at each pool top up.
The EPA limit for manganese in mains water is so low that manganese will not be a problem if mains water is used in the swimming pool. Manganese can cause problems in swimming pools near to manganese processing plants, or pools that are fed from wells that may contain traces of the mineral.